How Cultures Move Across Continents

They may look like flight paths around North America and Europe. Or perhaps nighttime satellite photos, with cities lit up like starry constellations.

But look again.

These animations chart the movement of Western culture over the past 2,000 years, researchers report Friday in the journal Science.

To make these movies, art historian Maximilian Schich and his colleagues mapped the births and deaths of more than 150,000 notable artists and cultural leaders, such as famous painters, actors, architects, politicians, priests and even antiquarians (people who collect antiques).

A shimmering blue dot lights up each new birth, while red dots represent each death.

We can watch as artists flock from rural areas to urban centers like London, Paris, Rome and Berlin after the Renaissance. Then in the late 17th century, people start to catapult from Europe into the eastern U.S. and then eventually leapfrog over to the West Coast.

"We're interested in the shape of the coral reef of culture," says Schich, of the University of Texas at Dallas. "We are taking a systems biology approach to art history."

After mapping the births and deaths, Schich and his team analyzed demographic data to build a model for how people and their cultural achievements ebb and flow across continents.

Right now the team has only maps for the U.S. and Europe. But Schich hopes to extend these visualizations beyond the Western world.

And the model isn't just fun to look at. The data also reveal trends and patterns in human migration over the past two millennia.

"From a very small percentage of the population ... we get out these general laws of migration that were defined in the late 19th century," Schich says.

One law was unexpected: People don't like to move too far from home, even in the 21st century. Despite the invention of trains, planes and cars, artists nowadays don't venture much farther from their birthplaces then they did in the 14th century. The average distance between birthplace and where a person dies hasn't even doubled in 400 years, the team found. (It's gone from 133 miles to 237 miles.)

Schich and his team also showed that deviations from these overall trends could be linked to historical events. For example, a lot of politicians and architects died in France between 1785 and 1805, right around the time of the French Revolution. But the violence had a much smaller effect on people in the fine arts.

The models are the latest application of a rapidly growing field, called network science which uses visualizations to find the underlying patterns and trends in complex data sets.

Several groups of scientists around the world have used networks science to map human migration. For example, physicists in Berlin analyzed the circulation of dollar bills to uncover laws of human travel, while a team in Boston examined mobile phone data.

Back in March, Nikola Sander and her colleagues at the Vienna Institute of Demography illustrated the flow of human migration over the past 20 years using U.N. census data from over 150 countries. The result is a beautiful interactive graphic, showing the major immigration routes around the world.

All these studies, Sander says, come with their limitations. In particular, the data typically represent only a select portion of the population those that spend cash, use mobile phones or are found in particular databases. And of course, most of us will never make it to a list of "notable artists."

But things get interesting, Sander says, when all these individual data sets point to a similar overall pattern. That's exactly what has happened here. The migration rules that Schich and his colleagues observed are similar to those found from looking at mobile phones and dollar bills.

"It's like little pieces of a puzzle." Sander says. "And it is nice if they come together to make a bigger picture."